LightSensitive

Light sensitivity, or photoreception, is the ability to detect light or respond to light stimuli. It applies to living organisms that perceive light and to man-made materials and devices designed to detect light.

In biology, light sensitivity is central to vision and non-visual light responses. In animals, photoreceptor cells in the retina—rods for low-light vision and cones for color and detail—convert light into neural signals. Non-visual photoreception, such as melanopsin-containing cells, helps regulate circadian rhythms and pupil size. In plants, photoreceptors including phytochromes, phototropins, and cryptochromes measure light quality, intensity, and duration, guiding processes like seed germination, stem elongation, flowering, and leaf movements. Many microorganisms also use light-sensitive proteins, such as microbial rhodopsins, to harvest energy or modulate cellular activity.

In technology, light sensitivity describes materials and devices that respond to light. Photodetectors, including photodiodes, phototransistors, and CCD/CMOS sensors, convert light into electrical signals. Photochromic materials change properties with light exposure, useful in sunglasses and smart windows. Photosensitive resists are used in semiconductor lithography to pattern circuits.

Applications span medicine, agriculture, imaging, environmental monitoring, and optogenetics. Design considerations for a light-sensitive system include spectral range, responsivity, noise, response time, and dynamic range.